Not sure if you have visited the Sanin region, but Izumo Taisha, Matsue Castle. Iwami Silver Mines, Adachi Museum are worth a visit. Bus Center about a 15-20 minute walk from Hiroshima Hilton.
This 500 yen bus might still be running then. It's a steal at that price. Hiroshima-Matsue 500 yen Bus
Onomichi is also a great little town to explore not far from Hiroshima City.